The above identified U.S. Pat. No. 8,728,361 discloses methods of making hollow spherical particles that are a composite of one or more elemental metals and elemental carbon. To make the hollow spherical particles, a dispersion of a precursor material in a liquid vehicle is formed and comprises at least one of (i) ions of the one or more metal elements and an organic ligand and (ii) a metal-organic ligand compound of each of the one or more metal elements. An aerosol of the liquid-dispersed precursor material is formed in a stream of inert gas, which is then heated to remove the liquid, decompose organic acid material and form porous, hollow spherical particles of a composite of the one or more metals and carbon.
FIGS. 3A-3C, 4A-4B, 5 and 6A-6B of the prior application (Ser. No. 12/828,353) are TEM images and depict hollow metal-carbon composite spheres that were formed from the as-disclosed aerosol-forming and thermal degradation process. As shown in these figures, the morphology of the particles is characterized by a densely porous metal-carbon exterior shell in the shape of a sphere that has a less-dense porous interior, such that the particles are characterized as “hollow.” The particles are characterized as hollow because of the less-dense porous interior within the highly dense spherical shell. The hollow spherical particles are typically smaller than one micron in diameter and have nanometer-sized pores in their interior.
As discussed in our co-pending application, very small porous particles have use in a wide variety of applications, such as, optical, electronic, magnetic, catalytic, and sensing devices ranging from photonic crystals to drug-delivery carriers. In certain applications, these porous spherical particles may be more advantageous than their bulk materials because their porous structure, which results in lower density, higher surface area, extra interior reaction space, and a reduced amount of material.